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Nicko

Fri Jun 11 2010, 09:47PM

Registered Member #1334 Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615

Is there a simple pros & cons table for the various primary topologies (pancake, solenoid, conical, inv-conical etc.)?

I like solenoid as its compact, but what might I be losing? (apart from my mind...)

Cheers

Nick

radiotech

Fri Jun 11 2010, 10:46PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

Since TC's work at frequencies akin to radio coils, it might be interesting to look at the geneology of coil forms of winding starting around 1920 up to the ferrite era.

You could weave a honeycomb form Tesla coil and then protect the design as an work of functional art

quicksilver

Fri Jun 11 2010, 11:51PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

This is a very interesting idea Nick.
- For that matter do such things exist for secondaries as well? I have seen the pancake design but have there been experiments with differences between tall thin coil as opposed to thick, wide secondaries (providing the basis of length & width of wire being same)?
Have "double coils" (two coils wound around the same tube column) been tested? Would two coils (2nd) on the same tube function?)
Could a Primary with BOTH pancake & helical provide any additional resource?
I have heard of Primaries within the Secondary; certainly there exists some general information re; the genealogy of both coil forms?

Sulaiman

Sat Jun 12 2010, 01:24AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Eventually I will get around to finishing what will probably be my last TC so I'm makng mental notes of all kinds of options,
one option that I want to investigate NEEDS a flat spiral primary;
I want to be able to turn the primary upside-down to investigate performance
(particularly sec - pri flashover etc.) with pri and sec wound in the same and opposite directions...maybe you want to try?

Other than that I think the type of TC will to a degree determine geometry,
e.g. conical for SGTC 'critical' coupling and helical for DRSSTC close-coupling.

radiotech

Sat Jun 12 2010, 01:25AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

Imagine the coil primary made up of these located inside the secondary tube:

You could make a nifty VTTC if you could just locate valves like these:

Wolfram

Sat Jun 12 2010, 01:30AM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

For larger tesla coils, the pancake configuration has the advantage of much lower risk of flashovers, while the solenoid configuration gives higher coupling, which is sorely needed in solid state coils with untuned primaries, and it's more compact. I'm sure others can elaborate further.

Anders M.

quicksilver

Sat Jun 12 2010, 03:41PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

radiotech wrote ...

Imagine the coil primary made up of these located inside the secondary tube:

Superficially I would imagine that placing the primary within the secondary would prevent flash-over & possibly be quite efficient. I know that it's been done & the results were good. Do you know any sound reason for a "one layer" winding on a secondary?
When examining various "tiny-coils" I noticed that the wire windings are uniquely thin. It seems much too thin to use a machine to wind them. But if two layers of 26 (or something other than micron sized wire) could be used; a small coil tube could be ample. If sufficient insulation were available, is it worth a try or are there reasons beyond that I am unaware of??

ScotchTapeLord

Sat Jun 12 2010, 04:01PM

Registered Member #1875 Joined: Sun Dec 21 2008, 06:36PM
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Posts: 635

A reliable insulator is the issue with internal primaries and multilayer coils...

radiotech

Sat Jun 12 2010, 04:46PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

The shape of a TC was initially a convenient design with high current windings at the base. Given that the mutual inductance is higher with close base coupling, and that per unit length of induction voltage should be higher on the bottom of the secondary than at the top, it would be nice to know if the current density is constant along the secondary tube.

If the entire thing is capable of producing an EM wave, at some point standing waves (unequal current density) will exist.

This model would be a single aircore transformer with another inductance in series with the secondary, whose voltage would be the product of the current (what is leaving the air-terminal at top) times the reactance of that upper section. That current should be in phase with current in the portion shaded by the primary but less because of the lumped induction diminished as it leaves the shadow.

As for the primary, it may have a distorted field load since its induction is mostly uncoupled beneath it.

This leads back to the original thread quandry. Is shape important?

I believe TI has developed a 3-axis magnetic and static chip used in magnetics to display what its 3 antennii sense with appropriate software.

HV Enthusiast

Sat Jun 12 2010, 09:18PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Very simply in a nutshell. . . for Tesla coil use . . .

Solenoid - Highest Coupling - Least Voltage Stand-off

Pancake - Lowest Coupling - Highest Voltage Stand-off

Inverse Conical - A bit lower coupling than solenoid - but has higher voltage stand-off than solenoid

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